Hines is getting greener and greener. The international real estate company has achieved LEED-EB, or LEED for Existing Buildings, certification for its 896,500-square-foot office building at 321 North Clark at Riverfront Plaza in Chicago. Hines took it up a notch. LEED Silver certification just wouldn’t do; the 35-story tower won the Gold.

The glass and stainless steel high-rise has hovered over the Chicago River since making its debut in 1987. Hines came into ownership of the asset in 2006 when Hines Real Estate Investment Trust Inc. snapped up the property.

Sustainable development is practically de rigueur, but transforming an existing structure into a green marvel is more of a challenge. However, it’s a challenge Hines does not hesitate to face. At 321 North Clark, the company incorporated a series of features to achieve the LEED Gold stamp, including low-flow aerators and water closets; efficient LED lighting in the lobby; and high-performing green cleaning services. Additionally, the building provides the option for tenants to minimize HVAC usage on weekends when space is not being occupied.

The tower stands above the rest, but not necessarily for its height. 321 North Clark also has an Energy Star rating of 83, which means it is 32 percent more energy efficient than the typical office building in the U.S.

“Achieving LEED Gold certification validates the diligent efforts by the on-site team to generate significant cost savings and environmental improvements for the long-term benefit of the tenants, owners and the city of Chicago,” Gary Holtzer, global sustainability officer with Hines, said.

The Chicago high-rise is hardly Hines’ first time at the rodeo. In December alone, the company’s Gateway Oaks I and IV office structures encompassing 204,700 square feet in Sacramento earned LEED-EB Gold certification, as did the 92,900-square-foot office building at 5820 Canoga Ave. in suburban Los Angeles.

Some of the best-known buildings in the country are taking the lead, so to speak, in the trend of transforming from less-than-efficient into shining examples of sustainability. The Empire State Building, benefiting from a $550 million rebuilding program that includes an energy retrofit, won LEED-EB Gold certification in September. The 2.9 million-square-foot, 1930s-era skyscraper is just one of a handful of National Historic Landmarks to earn the designation. In 2009, the owner of the Willis Tower, formerly Sears Tower, announced a $350 million sustainable modernization program for the 4.5 million square-foot office property, which is the tallest office building in the Western Hemisphere.